A ceramic porous body has been widely used for filters, catalyst carriers, and the like. For example, the ceramic porous body has been used for an exhaust gas purifying device provided in a heat engine such as an internal combustion engine or combustion equipment such as a boiler, a liquid fuel/gaseous fuel reforming device, a service water/sewage purification device, and the like. The ceramic porous body is generally obtained by adding a pore-forming agent to a ceramic powder, adding a binder, forming agent, water, and the like to the mixture, kneading the resulting mixture, forming the kneaded product into a specific shape, and firing the formed product. The pore-forming agent is used to increase pores in the ceramic porous body and control the size and the number of pores.
As the pore-forming agent used to produce the ceramic porous body, a resin powder or a carbon powder which is burned during firing has been generally used. However, such a powder increases the firing time or produces carbon dioxide or toxic gas during firing due to high combustible content.
In order to prevent the above problems, attempts have been made to use hollow resin particles such as a resin foam or water-swellable particles such as crosslinked starch as the pore-forming agent (e.g. patent documents 1 and 2). However, the hollow resin particles are easily crushed during kneading, deaerating, or forming, whereby desired pore-forming characteristics may not be achieved. In particular, when integrally forming a hard formed product or producing a formed product using a continuous forming machine, the hollow resin particles such as a resin foam exhibiting poor mechanical strength are easily crushed, thereby making it difficult to obtain a ceramic porous body with a high porosity. When using the water-swellable particles, a problem does not occur in which the particles are crushed. However, since the combustibles cannot be eliminated, a problem similar to that arising when using the carbon powder or the like occurs to a certain extent.
[Patent document 1] JP-A-2002-326879
[Patent document 2] JP-A-2003-238271